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Finding the Fourth Proportional to 28.20, 42.20 and 21.42

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Solution

The fourth proportional to 28.20, 42.20 and 21.42 is: 32.05

Step by Step Solution

  1. Step 1: Write the proportion equation
    28.20 : 42.20 = 21.42 : x
  2. Step 2: Convert to fraction form
    28.20/42.20 = 21.42/x
  3. Step 3: Cross multiply
    28.20x = 42.20 × 21.42
  4. Step 4: Simplify right side
    28.20x = 903.92
  5. Step 5: Solve for x
    x = 903.92/28.20
  6. Step 6: Final answer
    x = 32.05

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.